Modified the minimum length of param attribute on bigbluebutton room. fixes #736
Merge remote-tracking branch 'origin/Bug#736'
Fix validation regex for room's param (after 9b6dcc1bd5, refs #736)

Now that it allows params with 1 char only the regex has to be smarter.
It allows numbers, letters and '_' anywhere, but dashes never as the first
or last character.